diff --git a/src/Symfony/Component/Security/Core/Authentication/Token/SwitchUserToken.php b/src/Symfony/Component/Security/Core/Authentication/Token/SwitchUserToken.php
index e575999374..ccccb5b51c 100644
--- a/src/Symfony/Component/Security/Core/Authentication/Token/SwitchUserToken.php
+++ b/src/Symfony/Component/Security/Core/Authentication/Token/SwitchUserToken.php
@@ -59,7 +59,12 @@ class SwitchUserToken extends UsernamePasswordToken
      */
     public function __unserialize(array $data): void
     {
-        [$this->originalToken, $this->originatedFromUri, $parentData] = $data;
+        if (3 > \count($data)) {
+            // Support for tokens serialized with version 5.1 or lower of symfony/security-core.
+            [$this->originalToken, $parentData] = $data;
+        } else {
+            [$this->originalToken, $this->originatedFromUri, $parentData] = $data;
+        }
         $parentData = \is_array($parentData) ? $parentData : unserialize($parentData);
         parent::__unserialize($parentData);
     }
diff --git a/src/Symfony/Component/Security/Core/Tests/Authentication/Token/Fixtures/switch-user-token-4.4.txt b/src/Symfony/Component/Security/Core/Tests/Authentication/Token/Fixtures/switch-user-token-4.4.txt
new file mode 100644
index 0000000000..7b3f7c4092
Binary files /dev/null and b/src/Symfony/Component/Security/Core/Tests/Authentication/Token/Fixtures/switch-user-token-4.4.txt differ
diff --git a/src/Symfony/Component/Security/Core/Tests/Authentication/Token/SwitchUserTokenTest.php b/src/Symfony/Component/Security/Core/Tests/Authentication/Token/SwitchUserTokenTest.php
index 00f1ac984a..8138f76596 100644
--- a/src/Symfony/Component/Security/Core/Tests/Authentication/Token/SwitchUserTokenTest.php
+++ b/src/Symfony/Component/Security/Core/Tests/Authentication/Token/SwitchUserTokenTest.php
@@ -84,4 +84,18 @@ class SwitchUserTokenTest extends TestCase
 
         $this->assertNull($unserializedToken->getOriginatedFromUri());
     }
+
+    public function testUnserializeOldToken()
+    {
+        /** @var SwitchUserToken $token */
+        $token = unserialize(file_get_contents(__DIR__.'/Fixtures/switch-user-token-4.4.txt'));
+
+        self::assertInstanceOf(SwitchUserToken::class, $token);
+        self::assertInstanceOf(UsernamePasswordToken::class, $token->getOriginalToken());
+        self::assertSame('john', $token->getUsername());
+        self::assertSame(['foo' => 'bar'], $token->getCredentials());
+        self::assertSame('main', $token->getFirewallName());
+        self::assertEquals(['ROLE_USER'], $token->getRoleNames());
+        self::assertNull($token->getOriginatedFromUri());
+    }
 }